Limulus is a genus of horseshoe crab, with one extant species, the Atlantic horseshoe crab (Limulus polyphemus). One fossil species is currently assigned to the genus though several other species have been named, which have since been assigned to other genera.
Currently valid species include: Limulus polyphemus (Linnaeus, 1758) Limulus coffini† Reeside & Harris, 1952- Pierre Shale, United States, Late Cretaceous (Maastrichtian)
Doubtful species include:Dunlop, J. A., Penney, D. & Jekel, D. 2013. A summary list of fossil spiders and their relatives. In Platnick, N. I. (ed.) The world spider catalog, version 14.0 American Museum of Natural History, online at http://research.amnh.org/entomology/spiders/catalog/index.html Limulus nathorsti† Jackson, 1906- Jurassic, Sweden
Tentative species: "Limulus" decheni† Zinken, 1862- Paleogene, Germany (considered by some intermediate between Limulus and Tachypleus)
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